FlexJobs just did a state-by-state analysis of telecommuting based on Census data and found that Colorado, Vermont, and Oregon continue to top the list, as they have for the past five years.

They’re not alone. FlexJobs found that 3.9 million U.S. employees (2.9% of the total U.S. workforce) work from home at least half of the time, up from 1.8 million in 2005.

States that have seen a rise in the number of people working from home are Wyoming (nearly 30% more since 2013), Rhode Island (19.4%), and Washington, D.C. (18.2%).

[Map: courtesy of Flexjobs]The concentration of telecommuters in some geographic areas can be attributed to population density and resulting traffic, such as in the Denver and Austin metro areas where employers may be inclined to offer flexible work to save employees time traveling to and from the office.

Likewise, certain areas have large numbers of companies in industries that are more likely to offer telecommuting options such as professional, scientific, and technical services. Agriculture and mining industries are also seeing an uptick in telecommuting work, as more of these jobs have administrative components that can be done remotely.